Angela Merkel and four US presidents

German Chancellor Angela Merkel is making her farewell visit to Washington DC after nearly 16 years in office, during which time she has worked with four US presidents.

Her tenure ushered in a warm transatlantic friendship, marked by occasional spats over Germany's military spending, climate change and financial recovery policies.

Ms Merkel isn't running again in September's German parliamentary election, and this last White House bilateral could be a litmus test for both nations going forward.

Video produced by Man Sum Lai and Alexandra Ostasiewicz.